Our objective is the use of NMR to learn about the mobility and relative orientations of groups in polypeptides, and thereby determine the conformations of these molecules in solution. The results of the NMR0 experiments will be combined with those from conformational energy calculations, to reduce the ambiguities present in both techniques. NMR studies will be carried out on vasopressin, oxytocin, enkephalin, gramicidin S, actinomycin D, and on various synthetic model polypeptides, each of which is designed to answer a specific conformational question. Also EPR studies will be carried out on spin-labeled ribonuclease to determine the pathway(s) of folding of this protein from the unfolded form (both with and without the disulfide bonds intact).